#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
double  menu(int  a)
{
	if (a==1)
		return a;
	else
		return a * munu(a - 1);

}
int main()
{
	int a = 0;
	double ret;
	scanf("%d", a);
	ret = menu(a);
	printf("%d", ret);
	return 0;
}